CHIBA, Japan - The pesticide found in frozen Chinese dumplings linked to the illnesses of 10 people in Japan was not produced in Japan, sources say.

Police sources said the methamidophos pesticide found inside the Chinese products had considerable impurities, indicating it was not the nearly 100 percent pure form of the pesticide typically produced in Japan, the Kyodo News reported Sunday.

While Japanese manufacturers are able to create the pesticide will little to no impurities, a ban is in place in Japan regarding its use as an agricultural chemical.

The impure form of the pesticide was discovered on the dumplings after 10 people fell ill in the Chiba and Hyogo prefectures after ingesting the Chinese products.

The sources told the Kyodo News the pesticide found on those products will undergo extensive examinations by the National Police Agency's National Research Institute of Police Science to determine if they are identical and where it may have originated.